The EGR is supposed to reduce Nitrous Oxide emissions. In places like LA under perfect conditions of high temp, temp inversion, low or no wind, all the planets aligned, and all the Pot Heads at the correct level of Buzz, smog can form. In the rest of the country where the dense cities are not built in a bowl, it does not happen. But like the Global Warming Theory that is being proven to have been a total fabrication of false data, the EPA enforces what they think the regulations may be. Regulations made up by Lawyers (Lawyers see every thing in shades of gray) who are lied to by so called Scientists who want grant money (academic welfare) and make up crap with out doing the proper pier review. Anyone who does what a True Scientist is obligated to do and Question the findings, is ridiculed and cut off form any funding. Most of the True Scientists will come out of the Academic Welfare Closet when they retire, unfortunately they do not live long enough to challenge the BS. Corruption in the so called Environmental Scientific Community is as bad as the Court Clowns that kiss up to a Third World Despot like Kim Jung Il, or the Mayor of Chicago, Rich Daily.
Agriculture, yup our veggie crops, produce Nitrous Oxides, the Waste Water Plants produce Nitrous Oxide, but in the EPA's infinite wisdom, they don't ban veggie growing or Waste Water Plants in cities like areas like LA.
The next move is DEF or Urea that will be injected into the exhaust, it is coming up as a mandate even for the gassers.
With the way things are going with the EPA if they are not reigned in, veggie growers will need training licensees and fill out a bunch of paper work to grow a garden, Nazi Like Nitrous Oxide Abatement Officers will be patrolling neighborhoods asking to see permits and papers.
I had a customer in a plating factory had to send off their Lemela Gravity Settler to have the contamination in the tank cleaned out because the truck driver did not properly tarp the unit. Who would think that washing a tank out that had road dust would produce waste water that could not be discharged into a Chicago Sewer with out going over the permit level.
Like I said, the EPA needs to be reigned in and have their power placed in check. if not you better do a great job of hiding your compost so the CO2 abatement Officers don't arrest you.
The EGR valve is stupid and evil for diesel engines. GDE Tune greatly reduces its' function and SEGR & ORM shuts it off.
Turbo Tim passed his emissions test with flying colors, need I say more.